Is camphor harmful to health

Answer 1

This is an extremely interesting question. On the one hand, camphor is widely used (eg in nasal inhalers and muscle rubs) with no apparent ill effects. On the other hand, every year there are instances of children having fits and even dying from ingesting camphor.

(eg see
"Camphorated oil: still endangering the lives of Canadian children", J G Theis and G Koren, 1995).

The fatal dose is believed to be as little as 2g or less. Camphor can also cause a syndrome clinically indistinguishable from Reye's syndrome, except by liver biopsy after death.

("Chronic camphor ingestion mimicking Reye's syndrome.", Jimenez JF, Brown AL, Arnold WC, Byrne WJ., 1983).

Personally, and this is pure speculation, I wonder whether camphor might be an unrecognised cause of chronic nerve disorders such as MS (multiple sclerosis). The symptoms of chronic camphor poisoning are largely unknown, and since camphor is fat-soluble, presumably camphor and its metabolites might accumulate in fatty tissue such as myelin. Camphor is known to be capable of causing inflammation (after all, that's why it's used as a muscle rub; to cause mild localised inflammation, bringing blood to the area), and MS is basically a chronic inflammation of fatty nervous tissue, leading to brain (white matter) and nerve damage.

MS is known to be more prevalent in northerly climes, where camphor is widely used as a nasal decongestant. The Canary Islands have an unusually high incidence of MS for their lattitude, but here camphor is grown commercially, I believe. It is known that MS is more common in people who have spent their childhoods in cool climates, and it's in such climates that mothers rub camphor-containing ointments on their children to help with cold and flu symptoms. This supports the idea that a steady accumulation of camphor during childhood is necessary for the subsequent development of nerve problems.

Camphor is traditionally used in cooking in parts of India and China, but data on nerve disorders are very lacking in these places.

OR .... this could just be rampant alarmist speculation on my part.

Basically camphor is a poisonous substance that is widely considered safe as long as you don't eat it or use it on damaged skin, or use large quantities of it. If you somehow absorb more than a gram of it, you definitely risk kidney and brain damage.